The cost of handling, transporting and disposing of semi-solid material in comparison to solid material is considerably higher, generally due to the specialized equipment required for safe handling. For example, a truck used to haul semi-solid material will require a sealed box to avoid seepage leaks, and will generally be fitted with a sealed top/cover to stop splashing liquid during transport. It is also generally known that landfill costs are higher for products that will not pass a liquids consistency test, for example a slump test or paint filter liquids test. Transporting solid material to a landfill is more environmentally sound as incidents during transport (i.e. vehicle rollover) are generally easier to manage. Compared to solids, liquids and semi-solid materials that spill during transport can have devastating environmental effects due to ease of spreading, as well as leaching into the ground.
Methods to convert liquid and semi-solid material into solid form suitable for disposal as conventional solid waste are known. Such methods involve the mixing of an additive to the liquid or semi-solid material to promote solidification. Traditional mixing/blending methods require batch mixing with devices such as pug mixers, mixing augers, or excavators/loaders that physically maul the two products together in a pit, tank or on the ground surface. With these traditional methods, “overdosing” is quite common, generally to address and compensate for poor mixing and clumping of the additive. In addition, the introduction of the additive to the semi-solid material is often complicated by dust issues that in itself presents a variety of health and safety concerns.